This invention relates to integrated optoelectronic devices comprising light-emitting field-effect transistors.
Organic electronic devices, such as light-emitting diodes, solar cells and field-effect transistors have become of interest for a range of applications in displays and electronics. Organic LEDs have advanced to become one of the most efficient light sources available, organic photodetectors and organic solar cells are capable of near 100% quantum efficiencies, organic-based biological, chemical and mechanical sensors and memory devices are being developed for a range of different applications. A recognized strength of organic devices is the ease with which different device functionalities can be integrated in a common materials platform. All these functionalities can in principle be realized using similar materials than can be processed using a common set of manufacturing technologies. Therefore, integration of multifunctional devices on a common substrate is simpler than, for example, for silicon based devices.
There is particular interest in integration of information processing functions realized used transistor devices and optical function with light generated by LEDs and detected by photodetectors. Integration of optical and electronic functions could be used in optoelectronic integrated circuits, in which a light signal that is generated in response to the outcome of some computations is coupled into a waveguide structure and send to a spatially separate part of the system in which it is detected and initiates another information processing function.
Similarly, electrically pumped lasing devices are of interest in which an electrically stimulated gain medium is incorporated into an optical feedback structure to achieve coherent light generation of well-defined wavelength by stimulating the emission of the gain medium. Electrically pumped lasers using organic semiconductors have not been realized yet, although optically pumped lasing has been achieved in a number of systems (Samuel, Chem. Rev. 107, 1272 (2007)). The reasons for this are related to additional optical losses that arc present when electrical pumping is used, due to presence of electrodes (losses due to absorption of light in electrodes), charge-carrier induced absorptions as well as presence of triplet states. At present no device architecture has been proven to be suitable realization of an electrically pumped organic semiconductor laser.
A common architecture for optically pumped organic lasers are distributed feedback (DFB) structures (Samuel, Chem. Rev. 107, 1272 (2007)), in which a 1-D or 2D periodic grating structure is integrated together with a film of an organic gain medium. Most DFB lasers reported in the literature so far are mostly etched into the glass substrate, and their feedback thus relies on the index contrast between the glass and the organic gain material deposited on top. A promising alternative approach is to include a thin layer of a material with a large refractive index (e.g, tantalum pentoxide Ta2O5, n=2.07) comprising the required feedback pattern, onto which the organic material is deposited (Harbers, Appl. Phys. Letters 87, 151 121 (2005)).
However, the aforementioned are limited and there exists a need in the art for additional improvements.